I have a decorator crab that does a good job of turning over the crushed coral. I also have a horseshoe crab that digs into the cc and therfore keeps it looking clean. The decorator crab is questionable for a reef tank, since they like to stick stuff on their backs, so far mine has used nothing but cc as his decorations. The horseshoe is pretty cool,but he only makes a public appearance every couple of days.
My hermit crabs(blue leg and scarlet) and all my snails tend to stay on the live rock,and dont' do much for keeping the cc clean.
I also have a couple of peppermint shrimp that do a little bit on the bottom, but they mostly hang out on the lr also.